JPS60233619A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain the titled thin, lightweight, image forming device at low cost without decreasing the resolution by reducing the thickness of the reflection structure of facing substrates. CONSTITUTION:A liquid crystal display panel is formed by laminating the 1st polarizing plate 40, a substrate 21 equipped with thin-film transistors (TR) 24 (24a-24d) for switching arranged in a matrix, a substrate 31 having a liquid crystal layer 36 and a counter electrode 32, the 2nd polarizing plate 41, and a diffuse reflecting plate 42 successively from the side of incident light I0. Then, the distance at which the incident light I0 reaches the reflecting plate 42 through the polarizing plate 41 is specified below display picture element pitch to prevent a reflected image from fogging.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus, and particularly to an image forming apparatus that can serve both as a display function and as an original for imprinting an electrophotographic image.

11. Conventionally, in image forming apparatuses having the above-mentioned functions, a simple matrix structure in which a large number of transparent stripe electrodes are arranged vertically and horizontally and sandwich liquid crystal therebetween has been used. However, this type of liquid crystal panel has the drawback that the amount of displayed information cannot be increased sufficiently due to limitations in the operating conditions of the liquid crystal. On the other hand, in recent years, as a means to increase the amount of display information, thin film transistors (T
PT) and a matrix configuration has been developed. However, increasing the amount of display information means that picture elements become smaller in an image forming apparatus with a fixed display area. When using this as a reflective type, there is an image forming part of the liquid crystal layer that is created by optical changes, and a shadow part that is created by projecting this optical change onto a light scattering and reflective surface. This had the drawback of producing a double image or two separate pixel images.

11511 The main object of the present invention is to eliminate the drawbacks of the above-mentioned conventional examples and to provide a high-quality image forming apparatus with a wide viewing angle and high contrast.

Another object of the present invention is to provide a thin, low-cost image forming apparatus having the above-mentioned functions.

The image forming apparatus of the present invention has been developed to achieve the above object, and more specifically, from the incident light side, it includes: a first polarizing plate; a switching thin film transistor arranged in a matrix; In a liquid crystal panel formed by sequentially laminating a substrate having a liquid crystal layer, a substrate having a counter electrode, a second polarizing plate, and a scattering/reflecting member, an interface where an electrode of the substrate having the counter electrode and the liquid crystal come into contact. and the distance between the surface of the scattering and reflecting member that causes scattering and reflection is equal to or less than the minimum pitch of the picture element electrodes that are repeatedly arranged.

The basic configuration of an apparatus system that uses the image forming apparatus (liquid crystal panel) according to the present invention as a display device and as a document for a copying machine will be explained below. FIG. 1(a) is a side view of the apparatus system in a display state, and FIG. 1(b) is a partially cutaway front view of the apparatus in a copying state.

In FIG. 1, a document table 2 is provided on the top surface of a typical copying machine main body 1, and at least the document corresponding surface 2a thereof is made of a transparent member such as glass.

A panel 3 according to the present invention is mounted on the document table 2 so as to be freely placed vertically. This panel 3 is shown in Figure 1 (
It can be used as a display by standing it up as shown in a). That is, like conventional liquid crystal display devices, reflective display can be performed using external light or separately provided illumination. On the other hand, if you want a hard copy of the displayed image, as shown in FIG. 1(b), place the display panel 3 face down so that it corresponds to the document-compatible surface 2a of the document table 2, and copy it in the same way as a normal document. do. In FIG. 1, 4 is a paper cassette, 5 is a paper output tray, 13 is copy paper, 6 to 12 are the internal structure of a typical copying machine, 6 is a photosensitive drum, 7 is a charger,
8 is a developing device, 9 is a transfer charger, 10 is a cleaner, 1
1 is a document illumination lamp, and 12 is a SELFOC lens array.

Further, the document table 2 may be of either a movable type or a fixed type, but the panel 3 is always fixed on the document corresponding surface 2a.

Particularly, in Fig. 1(b), an example of a movable document table type is shown for simplicity, but in the case of a fixed document table type, the document illumination and drum exposure optical system (here, 11 and 12) are replaced by the movable optical system. It may be a system.

When illuminating a document such as a normal sheet or book using the illumination lamp 11 in the optical system described above, the SELFOC lens 12 normally uses the SELFOC lens 12 to absorb specularly reflected light from the document (indicated by 14 in FIG. 1(b)). ) The structure of the optical system is such that it does not incorporate This is because when you incorporate specular reflected light,
This is because the reflected light from the document table itself is also taken in, making it impossible to obtain a copy image of sufficiently high quality.

That is, the image formed on the drum 6 is the scattered reflected light from the document surface.

Next, the configuration of the panel 3 used in this invention will be explained.

Fig. 2 is a perspective view of a substrate having a semiconductor drive circuit in which thin film transistors are arranged in a matrix, which is one of the components of the panel, and Fig. 3 shows a partial example of a liquid crystal display panel incorporating this. Shown as a cross-sectional view. That is,
The substrate shown in FIG. 2 is a substrate 21 made of glass or the like constituting a display panel, on which drive thin film transistors (hereinafter often referred to simply as rTFs) are arranged at a density of about 2 to 10 transistors/mm.
TJ) are arranged in a matrix. T.P.
T is the gate line 22aa and 2 formed on the substrate 21.
2ab (made of a transparent or metal thin conductive film), gate electrodes 22a, 22b, 22c provided on the gate line,
22d, and at least this part is AI, M, o, C
An opaque electrode made of a metal such as r is used. Thin film semiconductors 24.24b, 24c, and 24d formed on the gate electrode via an insulating film 23, a source line (made of a conductive film) 25.25b provided in contact with one end of the semiconductor, and the other end of the semiconductor. The provided drain electrodes 26a, 26b,
26C126d etc.

Further, FIG. 3 shows a liquid crystal display panel composed of the electrode plate shown in FIG. 2 and a counter substrate. In Figure 3, 3
1 and 21 are transparent substrates such as glass or plastic; 26
b and 26d are drain electrodes serving as the display unit described above;
2 is a counter electrode. 26c, 26d, etc., I n,
A transparent conductive film such as No. 203 or SnO2 is used.

25.25b are source lines, AI and Cr.
, Mo, Au, Ag, Pt, Pd, Cu, and other metals are used. 33a and 33b specifically show an example in which the insulating film is formed only on the gates of 22a and 22b, and 34
are insulating films provided as necessary; 22c, 24
d is a semiconductor such as CdS, CdSe, Te, or amorphous silicon, 35 is a spacer, and 36 is a liquid crystal layer.

When used in the TN mode, the surfaces of the insulating layers 34 and 37 are subjected to orientation treatment. For orientation treatment, these insulating layers themselves are diagonally deposited or have fine grooves in one direction, but other methods include forming a polymer film on the surface of this insulating layer. This can also be achieved by rubbing.

This display panel uses twisted nematic (T N
) display modes are available. The incident light IO to the display panel of this invention becomes linearly polarized light by the first linear polarizing plate 40 and enters the liquid crystal layer, and when no voltage is applied, this polarization plane rotates 90 degrees and reaches the second polarizing plate 41. .

The second polarizing plate has a polarizing plane arranged so as to transmit this polarized light.

That is, the first polarizing plate and the second polarizing plate are arranged so that their polarization planes are perpendicular to each other. Subsequently, the light is reflected by the scattering/reflecting plate 42 and returns to the incident light side, but the direction varies depending on the scattering/reflecting plate, resulting in a bright display. In the part where a voltage is applied between the upper and lower electrodes, the incident light is polarized by the first polarizing plate without changing its plane of polarization.
The light reaches the polarizing plate, where the light no longer passes through, creating a dark state.

Figure 4 illustrates the relationship between the part of the picture element that optically changes and the shadow part caused by this.
Only the arrangement of the optically functional parts is shown.

The thickness of the liquid crystal layer that changes optically is usually around 1 OIL, which is very thin compared to the substrate material.On the other hand, the two polarizing plates 40 and 41 that detect this optical change are placed opposite the TFT substrate. They are arranged apart from each other by the length of the electrode substrate, and when detecting reflected external light, the light scattering plate is arranged further behind the second polarizing plate.

The obliquely incident light IO enters the liquid crystal layers 43a, 43b, and 43c in pixel units that cause optical changes. Now, if 43b is the voltage application part, the part indicated by A becomes dark,
Dark spots can be identified or detected against the background of the light scattered by the reflector 42.

On the other hand, the projection surface B of this A onto the reflecting plate 42 also becomes dark as a shadow. Therefore, the black spot to be identified or detected is the area where A and B overlap. This means that, compared to using only A as the distinguishable unit, B causes unnecessary blurring.

In the above example, when considering that the electrode pitch of the picture element is about 0.5 mm, the distance between the position of the liquid crystal layer 43b that shows optical change and the light scattering plate 42 that creates a reflected image is 0°5 mm, and the incident light If the incident light is inclined by 45'' with respect to normal incidence, then 43
The optical image b forms a shadow image completely shifted by one pitch. In reality, a smaller pitch, that is, a pitch of about 0.1 mm, is also created, and in this case, if the other conditions are as described above, a shadow image shifted by 5 pitches will be created.

In this invention, by setting the distance from the liquid crystal layer to the light scattering reflector via the second polarizing plate to be equal to or less than the display pixel pitch, the above-mentioned blurring of the reflected image is prevented and achieved. Provide the peripheral configuration of the opposing substrate for this purpose.

The distance from the interface of the counter electrode substrate with the liquid crystal to the reflective plate,
The reason for setting the ratio to the pixel pitch to be 1 or less is that, first, the above ratio of 1 is the limit at which the actual liquid crystal image and the shadow part are not completely separated by 45° incident light. It is. The second reason is that in the case of incident light at an angle of 45° or more, (i) total reflection of the incident light occurs. (11) The optical path length of the incident light is long, causing scattering and not producing clear shadows. (iii) When the incident angle is large, the polarization rate decreases and the shadow image becomes weak. This is because for any of these reasons, the influence of the shadow image becomes smaller.

However, for pickling, it is better that the above ratio is 1/2 or less, and in principle, the thinner the layer, the better.

The present invention is based on a configuration that can realize such conditions, and FIG. 5 shows the configuration of the counter substrate side shown in FIG. 3. Reference numeral 56 denotes a counter electrode in contact with the liquid crystal surface, and as described above, a transparent conductive film made of In202.5n02 or a thin film of gold that transmits light to some extent is used. 55 is a substrate that supports this transparent conductive film, and a transparent polymer film is preferably used in the present invention. - Examples include uniaxially oriented polyester, polyether sulfone,
Other materials that can be used include polycarbonate, polysulfone, urethane-modified polyorofil, and cellulose film. 54 is a polarizing film, which is connected to the transparent conductive film substrates 54 and 5 described above.
A so-called H III film supported by a substrate No. 3, ie, a polarizing film made of stretched polyvinyl alcohol dyed with iodine, is preferably used. In addition, a polarizing film dyed with a dichroic dye is also preferably used. The membrane 53 may be made of the same material as the material 55, but a transparent cellulose film or acrylic film is more preferably used. 52 is an adhesive or a pressure-sensitive adhesive layer, and 51 is an AI whose surface has a diffused reflection property.
It is a reflective plate such as. With such a laminated structure mainly made of polymeric materials, when a counter substrate integrally configured with a transparent electrode and a polarizing plate is used as the counter substrate shown in FIG. 3, the liquid crystal surface and the reflective surface can be adjusted within the range specified by the present invention. You get what you get.

゛That is, the height of the transparent electrode part 56 is 0.3gm, and the height of 55 is 25gm.
#Lm to loO#Lm, 54 polarizing film is 4k to 151Lm, 53 is also 25JLm-1OOJLm, 5
The pressure-sensitive adhesive layer of No. 2 can have a thickness of about 2 to 3 gm to about 10 JLm. Therefore, from the surface in contact with the liquid crystal of 56,
It is possible to obtain a reflection surface of about 50 pm to 200 pm.

Therefore, with such a configuration, it becomes practical to achieve a reflection configuration with a density of 20 lines/mm at maximum to about 5 lines/mm.

Of course, there is no problem with low-resolution images.

FIG. 5(b) shows another application example in which the thickness from the liquid crystal interface to the reflective layer is within the range allowed by the present invention in relation to the pixel pitch, and is formed on a polymer film of 55. The polarizing film 54 and the diffused reflection plate 51 sandwiched between the transparent conductive films 56, 55a, and the polymer films 53 are 52a, respectively.
, 52 are integrated by an adhesive or pressure-sensitive adhesive layer. In this way, it is sufficient to integrate the transparent conductive film, polarizing plate, and reflective plate, which were created by independent processes, and each function is not subject to process restrictions.

As explained above, according to the present invention, when using a TPT matrix substrate that can provide a large amount of display information at a minute pitch, the resolution can be improved by thinning the reflective structure of the opposing substrate. To provide an image forming apparatus that is thin, lightweight, and inexpensive, satisfying both display function and imprint function without deteriorating the performance. Furthermore, by constructing the counter substrate from a polymeric material, an image forming apparatus having excellent i-impact resistance from the back side can be obtained.

[Brief explanation of the drawing]

FIG. 1(a) shows an image forming apparatus (liquid crystal panel) of the present invention.
1(b) is a partially cutaway front view of the same device in the copying state, and FIG. 2 is a matrix of thin film transistors, which are one of the components of the panel. FIG. 3 is a perspective view of a substrate having a semiconductor drive circuit arranged thereon; FIG. 3 is a sectional view in the thickness direction of a liquid crystal display panel composed of the electrode plate and counter substrate shown in FIG. 2;
FIG. 4 is a schematic cross-sectional view illustrating blurring of a reflected image around the counter substrate, and FIGS. 5 (&) and (b) are cross-sectional views of examples of preferable counter substrate stacks used in the present invention. 21...TFT substrates 24a, 24b,...e eTFT thin film semiconductor 3
1... Opposing substrate 36... Liquid crystal layer 40... First polarizing plate 41... J second polarizing plate 42... Φ scattering reflection plate No. 11A (a) Fig. 1 (b) 20th 3rd rfJ 0

Claims (1)

[Claims] 1. From the incident light side, a first polarizing plate, a substrate having switching thin film transistors arranged in a matrix, a liquid crystal layer, a substrate having a counter electrode, a second polarizing plate, and a scattering/reflecting member. In a liquid crystal panel formed by sequentially stacking layers, an interface where an electrode of the substrate having the counter electrode and the liquid crystal come into contact;
An image forming apparatus characterized in that the distance between the scattering and reflecting member and the surface that causes scattering and reflection is equal to or less than the minimum pitch of picture element electrodes that are repeatedly arranged. 2. The substrate having the opposing electrode and the second polarizing plate,
The image forming apparatus according to claim 1, comprising a polymer material laminate.